Automatic telephone system



Nov. 4 1924. 1,514,193

w. A. BENSON AUTOMATI C TELEPHONE SYSTEM Filed J 26, 1921 2 Sheets-Sheet l OPERATOR? HEAD 5E7.

-Inuen ur W. A. BENSON AUTOMATIC TELEPHONE SYSTEM Nov. 4 1924.

Filed July 26. 1921 2 Sheets-Sheet 2 Inu"s n'lur hfilham .ELBsnsun .Z. rr-

and useful Improvements Patented Nov. 4, 1924.

ii. I 1E,

WILLIAM A. BENSON, OF CHICAGO, ILLINOIS, ASSIG-NOR TO AUTOMATIC ELECTRIC COMPANY, OE CHICAGO, ILLENOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPI-IO NE SYSTETIL Application filed July 26, 1921. Seriall No. 487,802.

To all whom it may concern:

Be it known that 1, WILLIAM: A. BENSON, a citizen of the United States of America, and a resident of Chicago, Cook County, and State of Illinois, have invented certain new in Automatic Telephone Systems, of which the following is specification.

The present invention relates to automatic telephone systems in general, but is concerned more particularly with such systems as include toll or long distance lines in addition to the local subscribers lines; and the object, broadly stated, is the provisionof novel and improved circuit arrangements to be used by a toll operator for connecting toll lines with local subscribers lines.

In a. modern automatic telephone system it is common practice to provide toll switches which, together with their inter-connecting trunk lines, form what is known as a toll service trunking system, through the medium' of which the local toll operator extends all toll calls, both incoming and outgoing, to the local subscribers lines. It is the usual practice to connect the toll lines with the toll service trunks by means of cord circuits. It is easily seen now that in such systems since every call, whether incoming or outgoing, must be extended by way of a toll line, a cord circuit, and a toll service trunk, aside from having them in reserve to take care of one or more getting out of order. nothing is gained by making either the toll service trunks or the cord circuits greater in numher than the toll lines, and vice versa. Accordingly an arrangement is contemplated whereby each toll service trunk line is made individual to a toll line, the cord circuits being replaced by permanently associated links which connect each toll line with a. toll service trunk line.

The above indicates in broad terms the scope of the invention, however, various features included in the working of the complete system will not now be specifically mentioned, but will be described fully in the course of thespecification and pointed out in the appended claims.

Referring now to the drawings, which comprise Figs. 1 and 2, in order to enable them to be understood best, Fig. 2 should be placeddirectly over Fig. l with the corresponding lines in alignment. lVhen laid out thus they represent diagrammatically sufficient of the equipment in the toll otlice, in a system of the type described, to enable the invention to be understood.

Referring now particularly to Fig. 1, the

toll line X, shown in the loter left-hand corner thereof, is one of a number of toll lines which may be terminated in the toll ollice of the system( As shown, the toll line X extends through, by way of the permanently associated link designated by the reference character O, and the automatic. repeater E,

to the talking conductors 89 and 91 of the toll service trunk comprising conductors 8991, inclusive. This toll service trunk is assumed to extend to and terminate in a toll first selector belonging to the previously mentioned toll service trunking system. Such a trunking system is completely disclosed in the United States patent toWicks No. lQMA/l, granted September 9, 1919.

Referring now to 2. the jacksJ and T u are associated withthe operators position at which the link circuit O is located and,

together with a small number of cord circuits of which the cord circuit 0 1s one, are

used for the purpose ofmaking emergency connections as will be hereinafter explained. The "yanks J and J which are multiples of the jacks J and J,respectively, are located at the i'iight operators position." This operator has a number ofcord circuits, each of which is a duplicate of the cord circuit 0,

by means of'whichshe connects the toll lines with thetoll service. trunks.

It has been found many times in actual practice that the nightv operator, who in many systems other duties toperform beside, ige fng toll calls, is likely to have need of a greater number of c-ordcircuits of ti e so-called loop diallingtype than she has of the so called simpler: or grounded impulse type of cord circuit. Assumingthat such is the case. all'the cord circuits are arranged for loop dialling and the repeater E, shown in Fig. 1,;is interposed between the jacks J and J and the toll service trunk comprising conductors 89 9l, inclusive, and

among other things translates loop dialling impulses into grounded i'n'ipulses.

The operators head set, which is shown in the upper part of Fig. 1, is provided with a set of listening and monitoring taps and is further arranged for loop impulse dialling when the operator is using a cord circuit and for grounded impulse dialling when the operator is extending a connection-by way of the link circuit or a similar circuit.

The apparatus, having been described more or less in general, will now be described in connection with a detailed description of itsoperation. Forthis purpose it will be assumed that a call comes in over the toll line X. In response to the ringing current coming over the toll line X, ring up relay 11, which is connected in bridge of the toll line X by way of the back contacts of armatures 22 and 23 and said armatures of cut-off relay 12, energizes and becomes locked up mechanically by an interlockingarrangement (not shown) betWeen the armature of the said relay l1 and the armature of cut-off relay 12. A structure of this nature is disclosed in the copending application of Erickson, Serial No. 461,760,1iled April 16, 1921. As a result of the operation of relay 11, it places ground 011 conductor 68 at armature 20, thereby lighting the busy lamp L associated with the link circuit 0 and also the busy lamps L and L associated with the jacks J and J respectively. A branch of this circuit extends by way of armature 21 of cut otf relay 12 and its resting contact, conductor 70, the spring of the lamp switching key associated with the jack J and its resting contact, conductor 69, and line lamp L to battery.

The operator, upon noting the lighted condition of the line lamp L, throws her key K into listening position,'thereby operating the springs 100 103, inclusive. Springs 101 and 102, upon being operated, connect the operators head set in bridge of the heavy talking conductors, while spring 103, upon being operated, closes a circuit tor release relay by way of the lower pair of contacts of the release push button P. A branch of this circuit extends to battery through the holding lamp L which becomes lighted.

Upon energizing, release relay 10 closes a locking. circuit for itself at armature 17 and at armature 18 closes the following circuit for cut-oil relay 12: from ground by way of armture 27 and its rest mg contact, armature 26 andits resting conat armature 24-.

to maintain the busy lamps L L and L lighted after the ring up relay 11, which is unlocked mechanically by the pulling up of cut off relay 12, has fallen back. a

The answering operator now converses with the calling operator and after ascertaining the desired number throws the key into calling position, thereby operating the springs 105-109, inclusive. Spring 109, upon being operated, closes a circuit for release relay 13 which, upon energizing, locks itself to ground at armature 25 through the upper pair of contacts of the release push button P, and prepares a circuit for the marginal supervisory relay 16 As a further result ofthe operation of key L ground is placed on conductor 64- at spring- 108 and its working contact, thereby closing a circuit for the calling device switching relay of the operators head set. Upon energizing, relay 5O removes the impulse springs of the calling device 5 from the loop control circuit comprising conductors and 61 and places it in the ground impulse control circuit which may be traced as follows: from ground by way of armature 53 and its working contact, impulse springs of the calling device S, working contact of armature 52 and said armature, conductor 65, spring 106 of key K and its working contact, conductor 85, and the resting contact of armature 44 and said armature, to the control conductor 90 of the toll service trunk comprising conductors 89-91, inclusive. This control conductor 90 extends to and terminates in the line relay of a toll first selec tor, the other terminal of the said line relay being connected to the ungrounded pole of the exchange battery. Accordingly the line and release relays of the said toll first selector immediately energize and prepare the switch for operation.

The operator may now manipulate the calling device S in accordance withthe digits of the desired number, whereupon the switches of the toll service trunking system are operated in the usual manner to extend the connection to the desired line.

After having finished dialling the number, the operator throws the key K to the opposite or ringing position, whereupon the springs 105- 109, inclusive assume normal position, the calling device switching relay 50 of the operators head set becomes deenergized, and the switch control circuit is transferred from ground, by way of con duotor 64c, to ground by way of armature 24 and its working contact and the marginal supervisory relay 16. Supervisory relay 16, upon energizing, closes a circuit for supervisory lamp L by way of armature 40 and its resting contact, and the said lamp becomes lighted.

As a further result of the throwing of key K to ringing position, ringing current is sent out over the established connection thereby ringing the called subscribers bell until the said key is returned to normal position.

lVhen the called subscriber answers the circuits of the automatic switches are automatically put into talking condition and in order to notify the operator, a high resistance is automatically inserted into the operating circuit, whereupon the marginally adjusted supervisory relay 16 deenergizes, extinguishing the supervisory lamp L The calling subscriber may now converse with the called subscriber, assuming of course that the calling operator has in the meantime extended the connection to the calling subscriber by way of the other end of the toll line X.

When the conversation is finished the two subscribers replace their receivers. When the receiver is replaced at the calledsubstation, the before mentioned high resist,- ance is removed from the control circuit, whereupon supervisory relay 16 energizes again and lights the supervisory lamp L Nhen the calling operator, or the operator that originated the connection, gets the disconnect signal from the calling subscriber, she momentarily projects ringing current out over the toll line X, thereby operating the ring up relay 14: which is connected in bridge of the toll line X by way of spring 100 of key K and its resting contact, and the working contact of armature 19 and the said armature of release relay .10. Upon energizing, ring up relay 14E removes at armature 26 a shunt which is normally around relay 15, whereupon relay energizes in series with cut off relay 12 and at armature 27 opens another point in said shunt, at the same time lighting the supervisory lamp L lVhen the operator sees the lighted condition of the supervisory lamps L and L she knows that the conversation is finished and that the subscribers have replaced their receivers In order to release the automatic switches and to remove the busy signal from the toll line X, the operator momentarily operates the release push button P, thereby unlocking the release relays 10 and 13. Release relay 10, upon deenergiaing opens its own locking circuit at armature 17, thereby preventing it from energizing again and extinguishing the holding lamp L. As a further result of the deenergization of release relay 10, it opens the circuit of cut ofl relay 12 at armature 18, whereupon the said out ofi' relay 12 and relay 15 deenergize. The supervisory lamp L together with the busy lamps U, L and if now becomes extinguished. Release relay 13, upon deenergizing, opens the switch control circuit at armature 24L, whereupon supervisory relay 16 deenergizes and extinguishes the supervisory lamp L As a further result of the opening of the control circuit, theautomatic switches are releasedin theusual manner. in extending the connection is now restored to normal and ready for another call.

lVe shall now assume that the toll operator is authorized to set up a connection which must be extended by Way of a toll line of the group to which the toll line X belongs. Assuming that the operator decides to use the toll line X, the said toll line being idle, as indicated by the unlighted condition of the busy lamp L the operator throws the key K into listening, position, thereby connecting her headset in multiple with the toll line; lighting the holding lamp L and operating the release relay 10 and cut of? relay 12 in the usual manner. As a result of the operation of cut off relay 12 the busy lamps L L and L obviously become lighted and the ring up relay 11 is removed from in bridge of the toll line.

The operator now throws the key K in such a direction as to project ringing current out over the toll line X, thereby operating the ring up relay on the other end of the said toll line. Then the operator on the otherend of the toll lines responds, the calling operator gives her the number and requests her to extend the connection to the called subscriber. I

The calling operator now extends the connection to thecalling subscriber, byway of the toll service trunk comprising conductors 8890, inclusive, in the usual manner. V

After the connection is completed the calling and called subscribers may converse with. each other as desired; and atthe termination of the conversation they both replace their receivers.

lVhen the receiver is replaced at the calling substation the supervisorylampL is lighted ina manner hereinbefore described.

When the operator notes the lighted con- All the apparatus used v dition of lamp L she momentarily operates the key K so as to send ringing current out over the toll, line to operate the disconnect signal on the other end, and releases the connection by momentarily operating the release push button P.

/ has been mentioned before the toll operator, in addition to a number of link circuits such as link circuit 0, is provided also with a small number of cord circuits such as cord circuit 0. Now in case one of the toll service trunks, the toll service trunk comprising conductors 89,'91, inclusive, for example, is temporarily out of order, the. associated toll line is not tied up, for the operator who may be provided with one or two extra toll service trunks may insert one plug of a cord circuit into the toll line jaclnsuch as the jack J, and insert the other plug of the cord circuit into the ack of one of the extra toll service trunks, which jack is similar to the jack J. It may be stated that each of the reserve toll service trunks may be equipped with only so much of the equipment shown in Fig. 1 as is necessary.

Assuming, for the purpose of illustration. that the operator receives a call over the toll line X and finds that the associated toll service trunk is out of order, she manipulates the push button P, thereby restoring the circuit condition of the relays associated with the link circuit 0 to normal and inserts a plug of a cord'circuit, the left hand plug of the cord circuit 0 forexample, into the jack J, whereupon the cut off relay 12 of the link circuit 0 is operated over the following circuit 2. from ground by way of the resting contact of armature 7 8 and the said armature, resting contact of armature 80 and said armature, upper winding of the marginally adjusted sleeve relay 75. upper left hand pair of contacts of the key K thesleeve of the plug and corresponding contact of the jack J, conductor 67,-and cut oif relay 12 to battery. -Cut off relay 12, upon energizing, removes the ring up relay 11 from in bridgeof the conductors of the toll line and closes a circuit for thebusy lamps U, L and L in the usual man- The marginally adjusted sleeve relay i 75, however is not able to energize owing to the high resistance of cut off relay 12.

The operator now inserts the other plug of the cord circuit 0 into the jack of one of the reserve toll service trunks and, since the said jack is similar in every respect to the jack J, for the purpose of illustration it may be assumed that the jack J is theone used. With the assumption as above noted, the marginally adjusted sleeve relay 75 of the cord circuit 0, and cut off relay 35 and relay 36 of repeater E energize in series, the combined resistances of relays 35 and 36 being lower than the resistance of cut off relay. 12 of the link circuit 0. Upon energizing, relay 35 disconnects the toll service trunk conductors 89 and 91 from the associated toll line and connects them to the heavy talking conductors of the acks J and J at armatures 39 and 41, and at armature 4O disconnects the supervisory lamp L Relay 36, upon energizing, prepares a circuit for relay 37 at armature 42 and at armature 47 places ground on sleeve conductor 86 by way of the following path: fro-m ground by way of the working contact of armature 4t? and said armature, resting contact of armature 18 and said armature,conductor 88, and the working contact of spring 93 and said spring to sleeve conductor 86, the effect of placing this ground potential on sleeve conductor 86 is to short circuit sleeve relay 75 of the cord circuit 0, which relay falls back. As a further result of the inserting of the plug into the jack J thespring 83 is forced into engagement with its associatedcontact, thereby closing the circuit of supervisory relay 16 of repeater D in series with the line relay of the toll first selector as follows: from ground by way of the low wound supervisory relay 16, conductor 87 working contact of spring 83 and the said spring of jack J, conductor 85, resting contact of armature 1 1 and said armature, and control conductor 90 to battery, by way of the line relay of the toll first selector. The line and release relay of the toll first selector now energize and prepares the switch for operation in the usual manner.

Supervisory relay 16, upon energizing, closes a circuit for relay 37 at armature 28. Upon energizing, relay 37 connects the impulsing relay 38 in bridge of-the conductors leading to the tip and ring contacts of the jack J, at armatures 43 and 4:5. Impulsing relay 38 immediately energizes over the bridge across the tip and ring conductors, of the cord circuit 0, including relay 76' and the upper winding of relay 77', and closes at armature a6 a shunt around armature lt and its resting contact. Since relay 38 is wound with fewer turns than relay 37 as can be readily seen, and since relay 3? is retarded by a heavier spring combination which has a stiff adjustment, the time that elapses after the circuit of impulsing relay 38 is closed at the working contacts of armatures 13 and 45 and before armature 4:4- breaks away from its resting contact, which owing to a special adjustment does not occur until armature 4 1 is almost fully operated, is sufficient to allow impulsing relay 38 to operate, thereby placing the shunt around armature 4:4: and its resting contact at armature 46 before the said armature 44 has been moved out of engagement with its resting contact. As a further result of the energization of relay'37, it removes the previously pointed out short circuit from the sleeve relay of the cord circuit 0 at armature 48, and the said sleeve relay 75 immediately energizes and at armature 79 closes the circuit of the lower winding of relay 77'. The current through the lower winding of relay 7? serves to assist the current flowing through the upper winding in series with relay 76' and impulsing relay 38 of the repeater E and the said relay 7'? energizes. Belay 77, upon energizing, closes a circuit for supervisory lamp L at armature 81 andthe said lamp becomes lighted. Relay 76 also is energized but does not perform any function at this time.

The operator may now throw the'calling device key K in such a direction as to operate the right hand springs thereof thus removing relay 76 and the upper winding of relay 7? from in bridge of the talking conductors, at the same time closing the following bridge across the said talking conduc tors: from the lower talking conductor of the cordcircuit O, by way oi the working contact of the lower right hand spring of key K and said spring, conductor 61, normally closed contacts controlled by armature 52 ot' the calling device switching relay 50, impulse springs of the calling device S, normally closed contacts controlled by armature 53, resistance 58 associated with the secondary winding of the operators induction coil, the secondary windings of the said induction coil, conductor 60, and the upper right hand spring of the key K to the upper talking conductor of the cordcircuit O. Relay 77 it may be stated is now maintained energized over its lower winding.

The operator may now manipulate her calling device S in accordance with the digits of the desired number, whereupon the interruptions produced in the circuit of impulsing relay 38 are reproduced in the control circuit, including supervisory relay 16 and control conductor 89, at armature 46, thereby operating the automatic switches so as to cause them to connect with the desired line in the usual manner. Supervisory relay 16, being slow acting maintains its armature attracted throughout the interruptions. After having finished calling the desired number, the operator restores the calling device key to normal position, thereby disconnecting the calling device S and her head set from the talking conductors and placing the relays 76 and 77 in bridge of the said conductors again.

The operator now throws the key K into ringing position, thereby operating the upper and lower right hand springs thereof with the result that ringing current is placed on the tip and ring conductors of the ack J and the resistance 92 is inserted into the sleeve conductor of the cord circuit. In the repeater E, the low wound marginally adjusted relay 36 falls back in response to the placing of resistance 92 into the circuit, but relay 35 is maintained energized. Upon falling back, relay 36 opens the circuit of relay 37 at armature 42. Upon deenergizing, relay 37 closes a multiple point in the control circuit at armature 44 and at armatures 43 and disconnects the tip and ring conductors of the jack J from the upper and lower windings of impulsing relay 38 and connects them to trunk conductors 89 and 91. Ringing current is now sent out over the trunk conductors 89 and 91 to ring the bridged bell at the called substation.

ture 42 closes the circuit of relay 37. Relay 37, upon'energlzing, shifts the tip and ring conductors of the jack J from the trunk conductors 89 and 91 to the upper and lower windings of relay 38 again, whereupon the said relayk 38 becomes energized.-

and'lowerwindings of iinpulsing relay 38' and connects up the trunk conductors 89 and 91 again at armatures 43 and 45.- As a further result of thedeenergization of relay 37 it places ground on sleeve conductor 86 at armature 48 by way of a previously traced circuit, thereby short circuiting sleeve relay of the cord circuit 0. Upon deenergizing, relay 75 opens the circuit of the lower winding of relay 77, whereupon relay 77 deenergizes and extinguishes the lamp L to give the operator answering supervision.

The calling and called subscribers may now converse with each other in the usual manner and when the conversation is finished they both replace their receivers.

When the receiver is replaced at the called substation the resistance of the control circuit is again lowered, whereupon supervisoryrelay 16 is again energized and at armature 28 closes the circuit of relay 37. Relay 37 upon energizing, connects up the impulsing relay 38 again at armatures 43 and 45, and at armature 48 removes the short circuit from around sleeve relay 75 of the cord circuit 0. Relay 75, upon energizing, closes a circuit for the lower winding of relay '77. Current is now flowing through both the upper and lower windings of relay 77 an'dthe said relay," upon energizing, lights the supervisory lamp' L to' give the operator a disconnect signal.

When the calling subscriber replaces his receiver, the usual disconnect signal is brought in 'to the operator in the distant exchange and she momentarily throws her ringing key, thereby projecting ringing current out over the trunk line X. This ringing current comes in through the tip and ring conductors of the jack J and passes through the upper winding of relay 77 and through relay 76. Upon energizing in response to this ringing current, relay 7 6 removes the shunt from around the lower winding of the marginally adjusted'sleeve relay 75, whereupon the said relay energizes in series with cut off relay 12 of the operators circuit 0, and, upon so doing, opens another point in the before mentioned shunt around its lower winding at armature 78, and at armature 79 closes a circuit the lighted condition of the lamps L and L,

knows that the conversation is completed and that. both the calling and called subscribers have replaced their receivers and she pulls down the connection.

When the plug is removed from the jack J relays 35, 38 and 36 ot the repeater E deenergize and the latter opens the circuit of relay 37 at armature 42, whereupon the said relay 37 deenergizes. Supervisory rel-ay 16 deenergizcs and the automatic switches release in response to the opening of the control circuit at spring 83 and its working contact. In the cord circuit G relays 75, 7 6, and 77 now deenergize and the supervisory lamp L becomes extinguished.

When the plug is removed from the: jack J, cut off relay 12 of the operators circuit 0 deenergizes and connets up the ring up relay 11, and sleeve relay of the cord circuit 0 deenergizes and opens the circuit of relay 77 at armature 79. Relay 77, upon deenergizing, opens the circuit of supervisory lamp L whereupon the said lamp becomes extinguished. The entire conneo tion is now released and the apparatus restored tonormal condition.

It will be noted that with the exception of the upper and lower right hand springs ofthe key K which constitute the monitoring key and the upper and lower left hand springs of the key K which constitute the listening key, the two ends of the cord circuit O are identical and either end of the said cord circuit operates equally'well in connection with a toll line ack-such as the jack J or a toll service trunk jack such as the jack J. It willbe explained now in a few words how either end of this cord circuit may be used to connect with a trunk which is arranged for reversed battery supervision. Taking the right hand end of the cord circuit 0, for example, if we assume that the repeater E has been arranged differently and that instead of the method of supervision that was described in the preceding call the said repeater had been arranged merely to reverse the direction of current flow in the tip and ring condu tors of the jack J upon the answering of the called subscriber the supervisory lamp L would have become extinguished upon the falling back of relay 77 which falls back, upon the reversal of current in its upper winding, owing to the fact that the current flowing in the said upper winding opposes that flowing in the lower winding. This method of supervision may be used in case the operator has any trunks multiplied into her position that are arranged to give reversed battery supervision.

In regard to separating one end of the cord circuit 0 from the other so as to talk to one subscriber after the connection is established without letting the other subscriber hear, it may be said that it is only necessaryto throw the key K in the one direction or the other depending'upon which subscriber the operator desires to converse with. In thelink circuit 0, however this same result is accomplished in a slightly diii erent manner. If we assume that the operator has a connection set up through the said link and that she desires to converse with the subscriber on the toll end, she throws the key K to calling position, which among other things, disconnects the right hand or local end of the link circuit 0, at springs 105 and 107. In case the operator desired to converse with the subscriber on thelocal end of the link circuit C without the knowledge of the subscriber on the toll end thereof, she may throw the key K in such a direction as to operate. the upper and lower right hand springs thereof th reby disconnecting the toll line from the link circuit 0.

Provisions have been made in both the cord circuit 0 and the link circuit 0, whereby the toll operator may listen in and supervise a connection without causing the subscribers to hear disturbing noises and without shunting too much talking cur rent away from its intended path When the key K of the link circuit 0, which is a combined listening and monitoring key, is thrown in such a direction as to operate the upper and lower left hand springs thereof the operators' head set is bridged across the talking conductors and ground is placed on the conductor 62, thereby operating relay 51 of the operators head sct. Relay 51, upon energizing, opens the primary windings of the operators induction coil at armature 57; disconnects the operators receiver from the mid point of the secondary winding at armature 56; and at armature 55 disconnects the lower terminal of the secondary winding of the induction coil from conductor 63 and connects it again to the same conductor through the operators re ceiver. It will be seen now that any cur rent in order to reach the operators receiver must pass through the upper and lower secondary winding of the induction coil in series and resistance 58, and since the primarywindings of the operators induction coil are open at this time there is a high impedance to voice currents. so that only a minimum. amount of the voice currents are shunted away from-their normal path when the monitoring key is thrown. When the, monitoring key is restored relay 51, deenergizes and restores the circuits in the operators head set to normal. The conditions are obviously the same when the key K of the cord circuit 0 is thrown to the monitoring position.

In case the operator wishes to listen in on the connection and finds that she is unable to hear well enough when the monitoring key is thrown and does not wish the talking parties to be disturbed by noises which may be present in switchroom, she throws the listening key in the usual manner after having short circuited her transmitterby operating the spring 59 associated therewith. This spring may be operated by either a key or a push button.

As has been mentioned before, the jacks J and J which are multiples of the jacks J and J are located at the night operators position. This operator has multipled into her position all the toll lines and all the toll service trunks that terminate in the several day operators positions, it being well known of course that as the usual thing the traffic is very much lighter at night than during the day and one night operator will suffice whereas several day operators are required. The night operator among other things must be informed when a call comes in over any toll line. This is accomplished by providing a lamp switching key for each toll line jack in the night operators posi-' tion. One of these keys is shown associated with the jack J and when operated disconnects the line lamp I! associated with the link circuit 0 and connects up the line lamp L associated with the jack J Having described my invention, I will point out in the appended claims what I consider to be new and desire to have protected by Letters Patent.

What I claim as my invention is:

1. In a telephone system, an operators switchboard, toll lines and local trunk lines terminating at said switchboard, a group of link circuits for connecting said toll lines and local trunk lines, each link circuit being adapted to connect only a particular one of said toll lines with a particular one of said local trunk lines, and'a second group of link circuits for connecting said toll lines and local trunk lines, each link circuit of the second group being adapted to connect any toll line with any local trunk line;

2 In a telephone system, a plurality of toll lines extending to a distant exchange, a plurality of toll service trunks for connecting with local subscribers lines. a plurality of operators link circuits permanently associating said toll lines and toll service trunks together in pairs, multiple jacks for said toll lines and tell service trunks, and a plurality of operators cord circuits through the medium of which said toll lines may be connected with toll service trunks other than the ones with which such toll lines are paired.

3. In a telephone system, a plurality of toll'lines extending to a distant exchange, a plurality ot local trunk lines, operatofis link ci.rc1iita:l()i* connecting said toll lines and local trunk lines, each link circuit beu ing individual to a particular toll line and to a particular local trunk line, multiple jacks for said toll lines and local trunk lines, and a plurality of cord circuits for connecting said toll lines and local trunk lines via jacks at the option of the toll operator.

4:. in a telephone system, a toll line extending to a distant exchange, a local trunk line, an operators link circuit individual to said tollline and local trunk line for connecting the two together, ringing key in said link circuit for signalling a distant operatortovobtain a desired toll connection, and a series of operator controlled auto matic switches for connecting said local trunk line with a local subscribers line.

5. in a telephone system, a toll line exten ding to a distant exchange, a local trunk line, an operators link circuit individual to said toll line and local trunk line for con necting the two together, a ringing key in said link circuit for signalling a distant oporator momma desired toll connection, a

series of operator controlled automatic,

switches for connecting said local trunk line with a local subscribers line, and supervisory signals in said link circuit controlled by the distant operator and by the subscriber on the local line.

6. In a telephone system, an operators switchboard, a cord circuit and a spring ack thereat, an automatic switch, a trunk terminating in one end in said jack and at the other end in said switch, a supervisory Signal associated with said cord circuit, a repeater interposed 1n said trunk, means 1ncludmg said cord circuit and said switch forextending a connection by way of said trunk line and repeater to a desired line, a

relay in said repeater, means responsive to ,the answering of the subscriber on said desired line tor operating said relay to alter the potential of the sleeve conductor of said jack, and means responsive thereto for opercontrolling said relay over the two sides of the section of said trunk between said switch board and said repeater in series to send impulses over said control conductor to operate said switch in extending a connection, a second relay in said repeater, and means for operatingsaid' second relay over said control conductor responsive to the answering of the called subscriber to disconnectsaid repeating relay from the talking 10 my name this 20th dayof July, A. D. 1921.

WILLIAM A. BENSON. 

